1. Field of the Invention
The present invention relates to a manufacturing method of a liquid ejection head, a liquid ejection head, and an inkjet printing apparatus, and more particularly to a manufacturing method of a liquid ejection head in which a slit is provided in a projection portion, a liquid ejection head, and an inkjet printing apparatus.
2. Description of the Related Art
Regarding a liquid ejection head for ejecting liquid at a high speed by giving an electric signal to a thermoelectric conversion element to thereby instantaneously boil liquid, integration of channels is easy but residual air bubbles might occur in a liquid ejection head. The residual air bubbles occur since air dissolved in the ink by heat generated by the thermoelectric conversion element is eluted and bubbles of the air remain in the liquid ejection head. In the case where the residual air bubbles are left as they are, that gives a bad effect to eject characteristics of the liquid and might cause deterioration in images.
Therefore, in order to suppress such residual air bubbles, there is known a technology of providing a projection portion on an inner surface of an ejecting outlet plate of the liquid ejection head (See the specification of Japanese Patent No. 4018272, for example). By providing the projection portion on the inner surface of the ejection outlet plate, a speed component can be given to a flow of ink in parallel with the ejection outlet plate, and the bad effect exerted on the ejecting of the residual air bubbles can be eased.
Furthermore, there can also be considered a technology in which residual stress in an ejection outlet plate of the liquid ejection head is eased by providing a slit in the projection portion. By providing a slit, the residual stress in the liquid ejection head caused by a heat history or the like of a manufacturing process of the liquid ejection head can be eased, and nozzle peeling caused by the residual stress in the ejection outlet plate can be suppressed. Particularly, in the liquid ejection head having a plurality of nozzle rows, there is a great concern that the residual stress in the ejection outlet plate is large in the central part of the outermost row and the nozzle is separated. By providing a slit in the projection portion, the residual stress can be eased, and occurrence of ejection outlet plate and substrate peeling can be suppressed. Furthermore, depending on ink in use, the ejection outlet plate might be swollen, but by providing a slit in the projection portion, stress caused by the swollen ejection outlet plate can be eased.
Incidentally, the slit provided in the projection portion is formed by patterning a mold material on a portion serving as a slit on a surface where a supply port penetrates, by coating an ejection outlet plate serving as an ejection outlet plate thereon, by exposing and developing it, then by penetrating the supply port, and by removing the mold material.
However, in a method of forming a slit in the projection portion, defective patterning might occur due to an insufficient adhesion force between the surface where the supply port is penetrated and the mold material serving as the slit, and thus a desired slit cannot be formed. The surface where the supply port is penetrated and its vicinity is a smooth surface because there is no thermoelectric conversion element or wiring pattern for sending an electric signal to the thermoelectric conversion signal, and thus there is no anchoring effect or the like and the adhesion force might be insufficient.
Furthermore, a substrate having a plurality of thermoelectric conversion elements is formed through a semiconductor process, but since the size of a semiconductor wafer is increasing, an external force generated during development of the mold material becomes large. Moreover, along with the increasing length of the liquid ejection head, the length of the slit in the projection portion also increases, and the external force generated on an end portion of the mold material becomes further larger. As described above, due to the increase of the size of the semiconductor wafer and the length of the liquid ejection head, the external force generated during development of the mold material becomes further larger and there is a concern that defective patterning in development of the mold material might increase.